Research On Damage Detection Techniques Of Steel-truss Bridge Based On Coupled Highway-railway Bridge Vibration Responses

Due to the large number of bridges in China,our country is facing many problems such as heavy old bridge detection,maintenance,reinforcement and prevention of bridge collapse.The traditional bridge damage identification mainly relies on regular manual inspection.However,this method has many limitations such as untimely damage detection,high work intensity,large workload,difficult to detect parts,and high cost.A specific method is needed to identify the damage of the steel-truss bridge,for its structural complexity and load diversity.The research of damage identification based on vehicle-bridge coupling vibration analysis for steel truss bridge structure of highway and railway is a new subject proposed in recent decades with the increasing construction scale of large-scale cross-sea bridges and the development of structural engineering research theory.It has important theoretical significance and practical value.The space coupling vibration finite element model of the vehicle-train-bridge system for Yellow River Railway Bridge in Binzhou,is established firstly in this paper,and the factors of vehicle-bridge interaction,bridge deck irregularity and track irregularity must be considered.Based on that,the dynamic response of the bridge under different working conditions considering vehicle and train loads can be obtained,and the vulnerable parts of the bridge are analyzed according to its mechanical characteristics,which is the foundation of the sequential research.Then,the sensitivity of vehicle-bridge coupling vibration response to damage is used to identify the unit damage of the bridge,and the influence of different parameters of the steel truss bridge on the damage identification results is researched.The results of this study :(1)In the case of train encounter,the working condition of reverse driving is more disadvantageous to bridge structure and more damaged than that of the same direction driving.There is a linear relationship between bridge displacement and peak acceleration and load.The dynamic response of bridge structure is very sensitive to span.When the vehicle is driving on the bridge,the deformation of the bridge is not only vertical,but also transverse.(2)The influence of multi-lane vehicle driving on bridges is more complex.A large number of experimental simulations are needed to get accurate conclusions.(3)When identifying the damage of bridges,it is inevitable to encounter the problem of choosing the measuring points.Choosing the more sensitive measuring points will get more accurate identification results.The sensitive points to the damage of bridges can be judged by the peak displacement and acceleration.(4)Unconstrained optimization is simple,direct and convenient,but its solution speed is slow and it is easy to identify false elements.Weighted average unconstrained optimization considers the influence of adjacent units in the actual situation,but the damage factor of the real damage element identified is smaller than the actual damage factor.The constrained optimization method is excellent in recognition accuracy and iteration speed.